1. Field of the Invention
The present invention relates generally to direct-type back light devices for liquid crystal displays, and more particularly, to a direct-type back light device for a liquid crystal display, which is easy to assemble and is constructed so that a plurality of fluorescent lamps are controlled by a single inverter, thus reducing power consumption.
2. Description of the Related Art
Recently, there is a growing tendency to increase the size of a liquid crystal display (LCD). As the size of the LCD is increased, a back light device having a large size and high luminance is required. Such a back light device, having the large size and high luminance, must be provided with a plurality of cold cathode fluorescent lamps and a plurality of inverters.
As shown in FIG. 1, a conventional back light device for the LCD includes a diffusion member 20 and a reflection member 40. A plurality of fluorescent lamps 30 are installed between the diffusion member 20 and the reflection member 40 to be arranged side by side. Further, light radiated from the fluorescent lamps 30 is reflected by the reflection member 40, and is irradiated to a panel (not shown) of the LCD through the diffusion member 20.
Further, as shown in FIG. 2, the conventional direct-type back light device for the LCD includes a plurality of inverters 50. A capacitor 51 is connected to an output terminal of each of the inverters 50, and each of the fluorescent lamps 30 is connected to the output terminal of an associated inverter 50. Further, a high voltage transformer 52 and the corresponding capacitor 51 are connected to the output terminal of each of the inverters 50.
However, as shown in FIG. 2, the conventional back light device for the LCD is constructed so that the number of inverters 50 is increased, as the number of the fluorescent lamps 30 is increased. Thus, the conventional back light device is problematic as follows.
The conventional back light device has a problem in that luminance thereof is not uniform, because there may exist characteristic differences between a plurality of inverters 50 or between a plurality of the capacitors 51 provided at the output terminals of the corresponding inverters 50. Further, the output voltages and frequencies of the transformers 52 provided at the output terminals of the corresponding inverters 50 are dispersed, thus leading to non-uniformity of luminance. In order to reduce the dispersion of the output voltages and frequencies, the back light device may additionally have a dimming circuit to control an optical output.
The conventional back light device has another problem in that operational reliability thereof may be deteriorated, due to the use of the plurality of inverters 50.
The conventional back light device has a further problem in that manufacturing costs thereof are increased, due to the use of the plurality of inverters 50.
The conventional back light device has still another problem in that the back light device includes the plurality of inverters 50, thus reducing operational efficiency of the back light device, and thereby increasing power consumption.
Further, the conventional back light device has still another problem in that assembility thereof is deteriorated, due to the use of the plurality of inverters 50 and electric wires.